Sometime prior to July 2017, changes were made to the USGS webserver that force the use of an encrypted HTTPS connection in place of HTTP to download the SRTM tiles. Version 1.13 adds support for HTTPS using Transport Layer Security (TLS) version 1.2. The USGS server does not seem to accept earlier versions of TLS.
Previous versions of TerrainTool were built using Java 6 because this was the highest version supported on Mac OS X at the time (2010). However, Java 6 does not support TLS1.2, forcing TerrainTool 1.13 to be built on Java 7. Oracle provide downloads for both Java 7 and Java 8 for OS X but be aware that there may be compatibility issues with legacy Mac systems.I'm keen to hear from Mac users about whether their systems support Java 7 or Java 8 because it would clearly be better for everyone if I could upgrade TerrainTool to be build on the latest and most secure version of Java.
This version bring support for the ASTER-2 dataset that has recently become available. This has the same resolution as the original ASTER data but the processing has resulted in fewer artefacts. Internally, the data format is the same as before but the filename e.g. ASTGTM2_N51W003.zip now includes a "2" to indicate that it is from the ASTER-2 dataset. Note: you can't just read the file and read it as though it came from the original ASTER dataset because the files inside the outer zip "wrapper" also have a "2" added to their names.
Previous versions of TerrainTool running under Windows placed the terraintool.properties and data directory in the same directory as terraintool.jar. Under unix-family operating systems, (e.g. Ubuntu, Debian) these files were created in the current working directory, wherever that happened to be. If the current directory already contained a sub-directory called "data", terrain data files were just added to it. This sometimes resulted in terrain data being added to unrelated data directories and, potentially, duplication of data.
The sections below explain where the data files and properties file will be located, according to whether you have the cross-platform version (default) or used an application installer under Ubuntu or Debian. If you already have data that has been downloaded from the SRTM or ASTER sites, you may want to copy these into the new data directory to avoid having to download them again.
If you downloaded TerrainTool as a "jar" file from the UBSS web site, you have the cross-platform version which is built to run under Windows, Unix family (Ubuntu, Debian, Solaris etc.) and OS X. By default, this version of TerrainTool creates the terraintool.properties and the data store in the .terraintool sub-directory of the user's home directory. For recent Windows versions, this would be something like c:\users\Mike\.terraintool or /home/mike/.terraintool on Ubuntu. Note that normally, Unix-family operating systems treat directories starting with "." as hidden - hence the sub-directory may not be visible.
Apart from downloading terraintool.jar from the UBSS web site, TerrainTool can also be installed as a pre-packaged application for Ubuntu and Debian (thanks to Wookey!). This is identical to the cross-platform version, except that the properties file and data directory are placed in a more unix-friendly location, as follows:-
If building TerrainTool from source-code, the file locations are easily customised by changing a single line of TerrainFrame.java and writing a class to implement the Pathnames interface. See Pathnames.java.